Conventionally, there has been known an assembled battery provided with a plurality of battery cells (see JP-A-2012-123905). To be more specific, such an assembled battery includes: a battery stack which is formed by stacking a plurality of battery cells in a predetermined direction; a pair of endplates arranged on both end surfaces of the battery stack in the stacking direction; and a binding bar which integrally connects the plurality of battery cells to each other by connecting the pair of endplates. In such an assembled battery, between the battery stack and the endplate, that is, between the outermost battery cell in the stacking direction and the endplate, a separator is arranged.
The endplate extends in the plane direction orthogonal to the stacking direction of the battery cells, and presses the separator to the outermost battery cell. In this case, the endplate presses the separator to the outermost battery cell with an approximately uniform force at respective positions in the above-mentioned plane direction.
The separator has a rectangular corrugated cross-sectional shape. Accordingly, when the separator is pressed to the outermost battery cell by the endplate, gas flow gaps are formed between the outermost battery cell and the separator. Although heat is generated by the battery cells when the assembled battery is used, the battery cells can be cooled by allowing a cooling gas to pass through the gas flow gaps.
When charge-discharge cycles of each battery cell are repeated in the above-mentioned assembled battery, an electrode assembly accommodated in the inside of a case of the battery cell is inflated so that a center portion of the battery cell (case) bulges. As described previously, the endplate presses the separator to the outermost battery cell with an approximately uniform force at respective positions in the plane direction. Accordingly, when the center portion of the battery cell bulges, a pressing force applied from the endplate to a peripheral portion of the separator toward the battery cell becomes small and hence, a cooling gas which passes through the gas flow gap is liable to be leaked to the outside.